1. Field of the Invention
The present invention relates to a tooth mobility measuring apparatus which measures the tooth mobility of a tooth to determine the state of the tooth.
2. Description of the Related Art
Tooth mobility measurement is done to diagnose a tooth and the state of a tooth (e.g., the state of periodontal tissue that supports a tooth). Conventionally, a subjective measuring method has been used in which the tooth mobility is grasped on the basis of inspection, palpation percussion, the moving states of teeth, and the like. This method however largely depends on the subjectivity of the operator. In addition, since this method gives importance to only the displacement amount of a tooth, properties such as the viscoelasticity of periodontal tissue may not be made clear. To objectively determine the tooth mobility, a tooth mobility measuring apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-279157 has been developed. As shown in FIG. 1, this tooth mobility measuring apparatus hits a tooth with a hammer 4, catches with a sensor 3 the variation of the tooth that fluctuates upon being hit, extracts the variation as an electrical signal, and calculates the tooth mobility of the tooth on the basis of the electrical signal.
FIG. 2 shows another apparatus. This apparatus causes a pick 26 to fly through a cylinder 29 using the force of a spring 27 to make an impact on a tooth 28.
The conventional measuring apparatus described in Jpn. Pat. Appln. KOKAI Publication No. 4-279157 measures the acceleration of displacement of a tooth. The acceleration is measured by bringing the hammer into direct contact with the tooth, and the tooth mobility is measured on the basis of the acceleration. Hence, for accurate measurement, the hammering position on the tooth must be accurate. In addition, hammering must be done with an appropriate force. If the hammering force is too strong, the patient may feel a pain. The conventional apparatus shown in FIG. 2 executes automatic hammering. For this reason, the magnitude of load is stable, and the hammering force is unlikely to be too strong. However, patients whose teeth and periodontal tissue are not in a good state may feel pain upon hammering. Furthermore, since the acceleration of the hammer changes according to the tilt of the apparatus, the magnitude of load may change and influence the measuring accuracy.